Motivation, description, and summary status of geomechanical andgeochemical modeling studies in Task D of the InternationalDECOVALEX-THMC Project Page: 2 of 6
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Two generic repository types of similar
geometry are analyzed in Task D of
DECOVALEX-THMC (Figure 1). Both feature a
multibarrier approach relying on an engineered
barrier (e.g., waste, canister, buffer, tunnel) and a
natural barrier (rock mass). Repository Type A is a
simplified model of the Yucca Mountain site, a
deep unsaturated volcanic rock formation with
emplacement in open gas-filled drifts. In this case,
the open drifts provide a natural capillary barrier
that can limit liquid water entry from the densely
fractured formation. Repository Type B is located
in saturated crystalline rock; emplacement drifts
are backfilled with a low-permeability buffer
material such as bentonite (a concept considered in
many European countries and in Japan). Since the
sparsely fractured crystalline rock formation
surrounding the repository is saturated with water,
the tight (low-permeability) bentonite is necessary
to prevent water flow and solutes from coming into
contact with the waste canister. There is also a
difference in the amount of heat and temperature
rise. Type A considers a heat load that will result in
above-boiling temperatures within the tunnels and
in the near field rock. In bentonite-backfilled
repositories (such as Type B), the temperature is
generally kept below 1000C to prevent chemical
alterations of the bentonite material.
3. RELEVANT POCESSES
3.1 THM Processes
Significant geomechanical alterations are
expected to occur in response to the heat output of
the decaying radioactive waste. The strongest
effects coincide with the period of the highest
temperatures; i.e., depending on the repository type,
during the first decades or centuries after
emplacement. For example, in Type A, the boiling
of water creates a dryout zone in the near-field rock
that will prevent liquid water from entering the
drift for several hundred to a few thousand years.
In Type B, the drying and wetting of the bentonite
induces shrinkage and swelling in various part of
the buffer, with resaturation expected to occur
within tens of years.
At the same time, thermally induced stresses act
upon pre-existing fractures, which open or close
depending on the local stress. One of the most
Table 1: Research teams and simulators applied within DOE's DECOVALEX task
Research Team Simulator Coupling Mechanical/Chemic Hydraulic and Transport Model
DOE/LBNL (USA) TOUGH-FLAC THM Elastic, Elastoplastic, Discrete, single or dual continuum;
Viscoplastic multiphase liquid and gas flow
DOE/LBNL (USA) ROCMAS THM Elastic, Elastoplastic, Discrete or single continuum; unsaturated
Viscoplastic liquid flow; thermal vapor diffusion
BGR/Center for Geosys/Rockflo THM Elastic, Elastoplastic, Discrete or single continuum; unsaturated
Applied Geosciences w Viscoplastic liquid flow; thermal vapor diffusion
CAS, Chinese FRT-THM THM Elastic, Elastoplastic, Discrete or single continuum; unsaturated
Academy of Sciences Viscoplastic liquid flow; thermal vapor diffusion
JAEA, Japan Atomic THAMES THM Elastic, Elastoplastic, Discrete or single continuum; unsaturated
Energy Agency Viscoplastic liquid flow; thermal vapor diffusion
DOE/LBNL (USA) TOUGHREACT THC Equilibrium and kinetic Discrete, single or dual continuum;
mineral-water-gas multiphase liquid and gas flow;
reactions, HKF activity advection/ diffusion of total
model concentrations (sequential)
BGR/Center for Geosys/Rockflo THC PHREEQC Discrete or single continuum; unsaturated
Applied Geosciences w with liquid flow; thermal vapor diffusion;
(Germany) PHREEQC advection/ diffusion of total
JAEA, Japan Atomic THAMES with THMC PHREEQC Discrete or single continuum; unsaturated
Energy Agency Dtransu-3D-EL liquid flow; thermal vapor diffusion;
and PHREEQC advection/ diffusion of total
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Birkholzer, J.T.; Barr, D.; Rutqvist, J. & Sonnenthal, E. Motivation, description, and summary status of geomechanical andgeochemical modeling studies in Task D of the InternationalDECOVALEX-THMC Project, article, November 15, 2005; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc900314/m1/2/: accessed June 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.